Fig. 1. Hardware architecture of on-chip micro-ring resonator temperature sensing system. (a) Laboratory setup for the micro-ring resonator temperature sensing experiment; (b) portable device system development diagram; (c) specific hardware function block diagram of portable device

Fig. 2. Design scheme for DFB laser driver board. (a) Current feedback control circuit for DFB laser; (b) TEC temperature control circuit of DFB laser; (c) physical DFB driver board

Fig. 3. System control board design. (a) Hardware circuit design of the control board; (b) physical diagram of the system control board

Fig. 4. Physical diagram of device hardware. (a) Schematic of the micro-ring; (b) microscopic enlarged photo of packaged optical chip (30× magnification); (c) hardware connection diagram; (d) internal view of assembled device; (e) front view of portable device

Fig. 5. Temperature information corresponding to the micro-ring at different temperatures. (a) Temperature interface calculated from the mode position at a set temperature of 23.50 ℃; (b) temperature interface calculated from the mode position at a set temperature of 29.00 ℃; (c) resonant mode waveform interface at a micro-ring temperature of 23.50 ℃; (d) resonant mode waveform interface at a micro-ring temperature of 29.00 ℃

Fig. 6. Overall software architecture. (a) Control board software architecture; (b) driver board software architecture

Fig. 7. Flow chart of data acquisition and processing program for resonance mode. (a) Collection process diagram; (b) data processing flow

Fig. 8. Performance testing of the driver board. (a) Current stability curves of the DFB laser at 100 mA and 200 mA injection currents; (b) heating and cooling curves controlling the DFB laser at different temperature variations; (c) heating and cooling curves controlling the WGM micro-ring at different temperature variations

Fig. 9. Temperature sensing performance of the portable device. (a) Relationship between micro-ring resonator mode position and temperature at different laser bias currents; (b) temperature response rate of the coupled and packaged Si₃N₄ micro-ring resonator; (c) transmission spectra of Si₃N₄ micro-ring resonator at different temperatures; (d) relationship between resonant mode position and temperature change during the heating and cooling processes of the micro-ring at laser temperatures of 25.7 ℃, 25.9 ℃, and 26.1 ℃